1. Field of the Invention
The present invention relates to image display apparatus, and particularly relates to image display apparatus adopted in a navigation system and using real image data corresponding to a real image such as a satellite photograph or an aerial photograph of an earth's surface.
2. Description of the Related Art
A navigation system in the related art can display a map on a screen of a display unit on the basis of road map data stored in a DVD-ROM or the like, and further can display the position of the navigation system itself on the map or guide itself along a route to a destination on the basis of position data of the navigation system itself.
In the navigation system in the related art, however, a map image to be displayed is produced out of map data. Therefore, there is a problem that it is difficult to seize the current position of the navigation system itself through the map image or grasp the real circumstances around the current position of the navigation system itself.
This is because it is difficult to express the vertical position relation ship between roads over head crossing with each other on the map image, and in fact there are many roads and buildings not displayed on the map image.
As one of solutions to such a problem, there has been disclosed an invention in which the current position of the apparatus itself is displayed on an aerial photograph image made up from aerial photograph data (JP-A-5-113343). With such an aerial photograph image, it becomes very easy to see a building or the like as a landmark. Thus, it also becomes easy to seize the current position of the apparatus itself. In addition, there is an advantage that it can be also made easy to grasp the real circumstances around the current position of the apparatus itself.
However, in any case, it is not easier to seize the current position of the apparatus itself by an aerial photograph image made up using aerial photograph data than by a map image made up using map data. In addition, it is not easier to grasp the circumstances around the current position of the apparatus itself by the aerial photograph image than by the map image. It may be still easier to seize the current position of the apparatus itself by the map image than by the aerial photograph image.
Accordingly, it is anticipated that there will prevail next-generation navigation systems not using only aerial photograph images or only map images in the related art but using both the aerial photograph images and the map images. To this end, it is anticipated that it will be important in the future to appropriately use a real image such as an aerial photograph image and a map image having two different characteristics from each other.